Automated flagger

ABSTRACT

An automated flagger particularly suited for use as a marker in sequentially designating the location of each successive path of a series of paths traversed by an aircraft engaged in so-called crop-dusting activities. The flagger is characterized by a readily detectable, displaceable marker and an intermittently operable, stationary winch attached to the marker and responsive to radio signals for advancing the marker in uniform increments so that the pilot of the aircraft can repeatedly reposition the marker, through a transmission of radio signals, and readily discern the location of each successive path to be followed in making sequential passes over the area.

United States Patent [191 Taylor et al.

[ 51 Apr. 10, 1973 AUTOMATED FLAGGER inventors: Hugh C. Taylor, PO. Box385, Five Points, Calif. 93624; William A. Gunnarson, 1043 Adams, LosBanos, Calif. 93635 Filed: Mar. 28, 1972 Appl. No.: 238,815

US. Cl. "343/225, 340/1 14, 340/321 Field of Search ..343/225, 228;340/319, 321; 242/1293, 49

[56] References Cited UNITED-STATES PATENTS 1/1964 Lemm et a1 ..343/228X 6/l97l Grosz ..340/32l X Int. Cl ..'......G08 b 23/00, H04b 07/00Primary Examiner-Donald .l. Yusko Attorney-Herbert A. l-luebner et a].

[ 5 7 ABSTRACT of radio signals, and readily discern the location ofeach successive path to be followed in making sequential passes over thearea.

10 Claims, 6 Drawing Figures AIRCRAFT VOLTAGE TRANSMITTER I AIRCRAFT r,/R L Y D. c. GROUND BATTERY RECEIVER- I 38 SWITCHING TIMER CIRCUIT .J53 40 AUTOMATED FLAGGER BACKGROUND OF THE INVENTION The inventionrelates to flaggers for crop-dusting aircraft and more particularly toan'automated flagger which repositions itself in response to signalstransmitted from an aircraft, for marking sequential paths forsuccessive passes.

Often times, aircraft are employed in agriculture and are utilized tospray" or dust" various crops, including field crops and timber, withchemical insecticides, herbicides and the like. In such instances, it isparticularly desirable to operate an aircraft in a manner such that itlays down a substantially uniform pattern of spray or dust in order forthe operation to be effective in controlling various types of pestsincluding insects and diseases.

In order to achieve'the desired uniformity, the employed aircraft isflown in successive passes over a given area following laterally spaced,substantially parallel paths. The spacing between the paths preferablyis uniform and is determined, at least in part, by the width of eachswath made as the aircraft deposits a stream of dust or spray along thesurface of the area being treated. For reasons readily apparent, it ishighly desirable for each successive path to be well defined wherebyadequate distribution of the spray or dust is achieved as it isdeposited.

To achieve this end, it heretofore has-been common practice to provide aflagger with position indicators and station the flagger in a givenrelationship with each path to be followed during each pass over thearea beingtreated. As can readily be appreciated by those familiar withcrop-dusting activities, a flagger necessarily is subjected to adverseworking conditions since he continuously is engulfed in a spray or cloudof chemicals as the chemicals are discharged from the aircraft. This, ofcourse, results in an added economic expense.

The prior art, of course, is replete with fixed markers employed indesignating paths for aircraft and the like. Normally, such markersarefoundin the vicinity of tall obstruction airfields and the like andfrequently are utilized in permanently designating certain paths to befollowed by aircraft operating in the vicinity. However,

due to the fact that such markers serve as permanent OBJECTS AND SUMMARYOF THE INVENTION It is another object to provide a highly reliable,practical and economic automated flagger employable by those engaged incrop-dusting activities for designating the location of each path of aseries of paths prior to its being traversed by aircraft engaged indischarging, over given areas, predetermined quantities of dusts,sprays, and the like.

These and other objects and advantages are achieved through the use ofan automated flagger including an incrementally displaceable base,having projected therefrom a visually detectable flag and/or source ofradiation affixed to its distal end, attached to a line ex-- tended froma winch intermittently actuated inresponse to radio signals receivedfrom aircraft engaged in crop-dusting activities for designating eachsuccessive path to be followed by the aircraft in depositing swaths ofchemical sprays, dusts and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial view of anaircraft engaged in crop-dusting activities depicting relative positionsfor the'aircraft and components of the system which embodies theprinciples of the instant invention.

FIG. 2 is a top plan view of a winch employed by the system depicted inFIG. 1.

FIG. 3 is a sectional view taken generally along line 3 -3 of FIG. 2.

FIG. 4 is a sectional view taken generally along line 4-4 ofFIG. 2.

FIG. 5 is a perspective view of a displaceable marker employed by thesystem shown inFIG. 1.

FIG. 6 is a diagrammatic view, in single-line, block diagram form, ofthe system shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT throughout the several views,there is shown in FIG. 1

It is therefore an object of the instant invention to provide anautomated flaggerfor replacing signalmen in the course of conducting"crop-dusting" operations and the like utilizing low-flying aircraft.

It is another object to provide an automated flagger for aircraft whichis repositionable for sequentially designating paths for aircraftperforming crop-dusting an aircraft, generally designated 10, coupledwith an intermittently operable winch, generally designated 12, througha communication link, generally designated 14 As illustrated, the winch12 is coupled with a marker, generally designated 16, through a flexibleline 18. In operation, the line 18 is retracted, through an actuation ofthe winch 12, for advancing the marker 16 across a series of pathstraversed by the aircraft during crop-dusting operations. It is to beunderstood that the term crop-dusting is employed as a term generic'tovarious similarly conducted .activities including spraying, dusting andseeding of fields and timbered areas as well as grasslands and the like.

The winch 12 is housed within a suitable enclosure, generally designated20. Since the particular enclosure employed is varied, as desired, adetailed description of the enclosure 20 is omitted in the interest ofbrevity.

However, itis to be understood that the enclosure 20 is 3- The drum 22is mounted'on a laterally extended axle 28 which, in turn, is supportedby a pair of bearing blocks 30 arranged in juxtaposition with theopposite j parts driven rotation to the drum 22. In practice, the

As a practicalm'atter, the outputderived fromthe motor 24 is through anoutput shaft 36, to which is affixed the clutch 35 so that as drivenrotation is imparted to the output shaft, the clutch 35 is activated forthereby imparting rotation to theaxle 28 and hence to the drum 22. Itwill, of course, be appreciated that for the sake of simplicity indesign the output of the motor 24 is coaxially aligned with the drum 22.Hence, while notshown, it is to be understood'that the motor 24 isfixedly mounted upon an appropriate base, quite similar to the base 32.e

The particular motor utilized in driving the drum 22 is varied inaccordance with the available facilities and prevailing operationalrequirements. Therefore, while a D.C. (Direct Current) motor, havinghigh-torque characteristics, is particularly suited for use in drivingthe drum 22, other motors including appropriately geared synchronousmotors, or even gasoline motors,

.can be effectively employed for this purpose.

' his to be understood that the motor 24, as illustrated, iselectrically energized from a source of electrical energy, depicted as aD.C. battery, designated 38. The motor 24 is coupled with the battery 38through a suitable switching circuit 40 which serves to control theoperation of the motor by making and breaking an electrical circuitbetween the motor 24 and the battery 38. As a practical matter, theswitching circuit 40 has included therein a microswitch 42 coupled withthe motor 24 through one of a plurality of suitable electrical leads 44,FIG. 2, which are employedinselectively applying the voltage acrosswindings of the motor 24, in

a manner consistent with known principles of machine design techniques.The function of the switch 42 is to de-energize the motor 24 subsequentto a predetermined duration of activatiomlt is to be understood that theswitching circuit 40 is activated in response to an electrical pulseapplied thereto by a ground receiver unit 46 and is thus switched to anenergized mode for the thus completed circuit. The established energizedcondition of the motor 24 is maintained through the microswitch 42 untilsuch time as the microswitch isactuated for interrupting the circuitbetween the motor and the battery, in amanner hereinafter more fully setforth.

The ground receiver 46 is of a suitable design well 7 known to thoseengaged inthe electronic communication field and is provided with anantenna 48. This antenna serves to receive radio or electronic signalstransmitted from a radio transmitter 50 located aboard the aircraft 10.As best illustrated in FIG. 6, the transmitter 50 is coupled with asource of aircraft voltage 51 through a control switch 52, preferably ofa type including an actuator button mounted on the control stick of theaircraft.

Since the particular components employed in the switching circuit 40,the ground receiver '46 and the transmitter 50 form no specific part ofthe instant invention and the design of these circuits is well withinthe skill of the art, a detailed description thereof is omitted in theinterest of brevity. However, it is to be understood that thetransmitter 50 responds to a manipulation of the switch 52 and transmitselectronic signals along the link 14 to the ground receiver 46. Uponreceipt of the transmitted signal, at the receiver 46, the receiver 46is activated and responsively delivers an initiating pulse to theswitching circuit 40. The initiating pulse, in turn, serves tomomentarily close a suitable circuit component within the switchingcircuit 40, whereupon a voltage-derived from thebattery 38, is appliedacross the windings of the motor 24 for initiating the operationof themotor 24. Once the motor 24 is activated for driving the drum 22, themicroswitch 42 closes so that the energized condition for the motor 24is maintained through the microswitch. Hence, the motor 24 is energizedfor a 1 period determined primarily by the duration of the period duringwhich the microswitch 42 remains closed.

In response to the energization of the motor 24, the

drum 22 is driven in rotation through the clutch 3 5 whereupon the line18 is wound about the drum 22. The duration of the operation of themotor .24 is, in practice, controlled by the index sheave 26 about whichthe line 18 is passed, as the index sheave 26 serves to provide a motioninput to a timer 53, FIG. 6, which is employed to impose a cyclic modeof operation on the microswitch 42.

The sheave 26 is secured to a supporting a'xle 54 mounted for bothlinear and angular displacement by a pair of bearing blocks 56, alsomounted on the base 32, in a manner similar to that in which the bearingblocks 30 are mounted thereon. The axle 54 is extended through a thirdbearing block 58 suitably supported by a base 60 located within theenclosure 20. It should readily be apparent that the sheave 26 isrotated as the line 18 is tensioned and wound about the drum 22, due tothe fact that one turn of the line 18 is taken about the peripheryof thesheave 26.

The axle 54 has affixed thereto, in concentric relationship, a worm gear64. The worm gear 64 is of a known design and includes a helix, notdesignated, extending substantially the length thereof. Meshed with thehelix of the worm gear 64 there is a timing disk 66 having affixedthereto a laterally extended protuberance 68. Consequently, theprotuberance 68 is caused to describe a circular path as the disk 66 isdriven through 360 of angular displacement. As illustrated in FIGS. 3and 4, the microswitch 42 includes a switch actuating button 70 disposedin the path of the protuberance 68 so that the button is depressed uponbeing engaged by the protuberance for opening the electrical circuitbetween the battery 38 and the motor 24 for thereby de-energizing themotor.

In practice, the gear ratio established between the worm gear 64 and thetiming disk 66 is such that 360 of angular displacement imparted to thesheave 26 and, consequently, 360 of angular displacement imparted to theaxle 54 serve to impart 360 of angular displacement to the disk 66 sothat the button 70 is actuated once during each 360 of rotation of thesheave 26 for opening the circuit between the battery and the motor.Thus, the length of the line 18 wound about the drum 22 and the distancethrough which the marker '16 moves during each period of the motorsactivation are determined by the circumference of the sheave 26.Therefore, it is possible to advance the marker 16 through uniformincrements of travel, regardless of the effective changing diameter ofthe drum 22 about which the line is wound.

It is preferred that the axle 54 be subjected to Since the base 32remains stationary, relative to the housing, rotation of the worm gear64 causes the pivot pin 90 to describe a circular path whereuponrectilinear motion is imparted to the carriage 72 for therebymaintaining the worm wheel 86 and the timing disk 66 in continuousenmeshed engagement with the worm gear as concurrent angular andrectilinear displacement is imparted to the axle for simultaneouslyassuring that a proper placement of the line on the drum 22 is achievedand an increment of travel is imparted to the marker 16 affixed to theend of the line 18.

For enhancing detection of the marker 16, there is provided a staff 94,preferably of a flexible construction surmounted by a flag 96 and, ifdesired, a light 98. The staff 94 is seated in a suitable support 100,FIG. 5, mounted on a movable, saucer-shaped base 102 to which the line18 is attached at mutually spaced points 104. Because of itssaucer-shaped or convex disk configuration, the base 102 can readilyavoid various impediments and obstructions indigenous to the environmentin which the flagger is employed.

Of course, the staff 94 can be fabricatedfrom plexiglass or similarmaterial. Further, it is possible to employ a helical spring 106 as anintermediate section for the staff whereby the flag 96 and light 98achieve an oscillatory motion as the base 102 is advanced. The

rectilinear motion concurrently with its angular displacement in orderto cause the sheave 26 to perform a so-called level-wind function as theline- 18 is wound about the drum. It istherefore necessary for thetiming disk 66 to be moved along a rectilinear path in order to precludea disengagement thereof with the worm gear 64. In order to accommodatesuch movement, a carriage 72 is provided and seated in a'pair ofvertically spaced coplanar tracks 74, FIG. 4, and fixed to the axle 54through a pair of coaxially related bearings 76 disposed injuxtaposition with the opposite. ends of the worm gear 64.'The timingdisk 66 is affixed to the car riage 72 by a bearing pin 78, while themicroswitch 42 is coupled therewith through asuitable bracket 80. Thecarriage 72 is therefore advanced along a rectilinear path andtransports the timing disk 66 for purposes of continuously maintainingan enmeshed relationship between the timing disk 66 and the worm gear64. A pair of coaxially related fairings 79 is provided in a protectiverelationship with the opposite ends of the axle 54 for protecting theaxle during periods of "reciprocation operatively imparted thereto.

'Rectilinear motion of the axle 54 is effectedthrough the use of aPitman linkage, generally designated 82. This linkage includes a Pitmanarm 84 pivotally coupled at one end and projected from a worm wheel 86,which also is enmeshed with the worm gear 64. The opposite end of thePitman arm 84 is pivotally coupled with the base 32 by means of asuitable bracket and pivot coupling 88. As a practical matter, theopposite end of the arm is coupled with the worm wheel 86 through apivot pin 90 of any convenient design. The

purpose of accommodating an oscillatory motion of the flag and light isto accommodate ready recognitionof movement by the pilot, preparatory tohis making a pass. Due to the fact that dusting" frequently is performedat night, the light 98 can be intermittently energized foremittingradiation in a blink-ing" manner.- To

worm wheel 86 also is supported by the carriage 72. A

achieve this, a pair of switch contacts 108 are interposed between thelight 98 and a voltage source or DC. battery 110. Therefore, it shouldreadily be apparent that as the line 18 is wound about the drum 22 foradvancing the base 102 of the marker 16, the spring l06'permits thestaff to undergo deflection whereupon the contacts 108 areintermittently engaged and the light 98 is intermittently energized.

Accordingly, it is preferred that the light 98 be permitted to blinkonly in the event the marker 16 is being advanced by the winch 12 sothat a pilot readily is made aware of the fact that the marker 16 isbeing advanced in response to a signal transmitted from the transmitter$0.1m such instances, the staff 94 is sufficiently rigid .that thecontacts 108 will not be closed'so long as the marker 16 remainsstationary, but sufficiently flexible that the contacts repeatedly openand close in response to a flexing of the staff 94, as the base 102 isadvanced. Thus, a pilot will observe a continuous light when the marker16 is at rest and will observe a blinking light as the marker is beingmoved between successive positions. l

OPERATION receiver 46. This signal is employed in initiating an outputapplied to the switching signal circuit 40 for momentarily applying avoltage across the motor 24 whereupon the motor is momentarilyenergized. Once the motor 24 has been energized, the protuberance 68 isadvanced and removed from engagement with the button 70 of themicroswitch 42 for permitting a circuit to close between the battery 38and the motor 24,

whereby the motor is coupled 'with the battery 38- through themicroswitch. The drum 22 of the winch 12 is thus activated fordrawing-in or retracting the line 18. This retraction of the line servesto advance the marker 16 along the surface of the ground to a positionfor marking the path of the pilots next pass. As the marker 16 isadvanced, the staff 94 is flexed so that the pilot is made aware ofmovementof the base 102 as the marker 16 is advanced to its nextposition.

As the line 18 is wound about the drum 22, the index sheave 26 isresponsively rotated for driving the axle 54 in angular displacement.Rotation, or angular displacement, of the axle 54 drives the timing disk66, through the worm gear 64, in rotation for-thereby advancing theprotuberance 68 through the remaining portion of its circular path andinto switch-opening engagement with the switch actuating button 70 ofthe microswitch 42. Thus, the protuberance againv opens the circuitbetween the battery and the motor 24 so that the motor 24 is againde-energ'ized and the marker 16 permitted imparts rectilinear motion tothe carriage 72 to which the worm wheel 86 is fixed. As the carriage isreciprocated, the coplanar tracks 74 support the carriageagainstrotation. I

The aforedescribe'd cycle is again initiatedby a closing of the switch52 within the aircraft l whereuponthe motor 24 again is energized fortaking up the line 18, at the drum 22, for a period determined by theperipheral dimension of the index sheave 26 and the length of the pathdescribed by the protuberance 68 as the timing disk 66 is driven inrotation.

While the invention herein described has particular utility inoperations wherein aircraft normally are employed, it is to beunderstood that the invention is readily employable in any activitywherein a marker is to be incrementally advanced along the surface of agiven area. For example, the described embodiment of the invention canbe employed for identifying paths to be traversed by tractors and thelike engaged in performing various types of agricultural functions.

In view of the foregoing, it should readily be apparent that theautomated flagger of the instant invention provides a practical solutionto the problem of successively designating adjacent paths of a series ofpaths to be followed by aircraft during crop-dusting and similaroperations.

Although the invention has been herein shown and described in what isconceived to be the most practical and preferred embodiment, it isrecognized that depar comprising:

tures may be made therefrom within the scope of the invention, which isnot to be limited to the illustrative details disclosed.

Having described our invention, what we claimas new and desire to secureby Letters Patent is:

1. An automated flagger for aircraft engaged in activities wherein theaircraft is caused to over-fly a series of paths extended in parallelismacross a given area A. a marker for sequentially designating thelocation of eachpath of said series of paths; and

B. means responsive to electrical signals for successively repositioningsaid marker.

2. The flagger of claim 1 whereinsaidmarker includes a displaceablebase, a staff upwardly projected from the base and a visually detectableflag affixed to the distal end thereof.

3. The flagger of claim 1 wherein said marker includes a displaceablebase, a staff formed of a flexible material upwardly projectedfrom thebase, and a radia- ,tion emitter affixed to the distal end of saidstaff.

4. The flagger of claim 1 wherein said means for repositioning saidmarker comprises:

A. a fixed base;

B. a winch mounted on said base including a drum and an intermittentlyoperable drive train for imparting intermittent driven rotation to saiddrum;

C. a line extended from said marker and attached to the drum of saidwinch, whereby the line is incremently wound about the drum as rotationis intermittently imparted thereto; and i D. control means coupled withsaid drive train fo controlling the operation thereof.

5. The flagger of claim 4 wherein said control means includes a signaltransmitter mounted aboard the aircraft, a signal receiver mounted onsaid base, -a switching circuit connected with said receiver and saiddrive train, including means responsive to a received signal foractivating the drive train.

6. The flagger of claim 5 wherein said control mean further includestiming means coupled with said drive train for deactivating the drivetrain at the expiration of a predetermined period of activation.

7. The flagger of claim 6 wherein said timing means comprises:

A. a sheave'of a preselected diameter supported for intermittentrotation between said winch and said marker and having said line trainedabout the periphery thereof, whereby linear displacement of apreselected length of said line serves to drive said sheave through acomplete revolution of angular displacement as the line is wound aboutthe drum;

sheave support means including an axle and means securing said sheave tosaid axle, whereby the axle is driven in concurrent angular displacementwith said sheave, bearing means supporting said axle for simultaneousangular and linear displacement, and means responsive to angulardisplacement of said sheave for cyclically imparting rectilinear motionto said axle; and.

C. means responsive to an angular displacement of said sheave forinterrupting said switching circuit, including a rotatable timing diskhaving peripheral teeth, drive means having a worm gear mounted on theaxle and meshed with the teeth for driving said disk in rotation,'aprotuberance projected from the disk adapted to describe a circular pathas rotation is imparted to the disk, and an actuatable microswitchconnected within said switching circuit, including a switch actuatorinterposed in the path described by said protuberance and engagedthereby as the disk is driven in rotation, whereby the switch isactuated once for each revolution of said sheave.

8. The flagger of claim 7 wherein said means for cyclically impartingrectilinear motion to said axle includes:

A. a worm wheel meshed with said worm' gear and supported forrectilinear motion along a path paralleling the longitudinal axis ofsaid axle; and

B. a Pitman arm having one end thereof pivotally fixed to said firstworm wheel near the periphery thereof and the opposite end thereofpivotally coupled with said bearing support, whereby rotary motionimparted to said sheave as the line is wound about said drum isconverted to rectilinear motion and imparted to said axle.

9. An automated flagger for vehicles engaged in activities wherein avehicle is caused to traverse a series of substantially parallel paths,comprising a marker and means responsive to radio signals transmittedfrom the vehicle for imparting uniform increments of travel to saidmarker.

10. The flagger of claim 9 wherein said means includes a line attachedto the marker, means including a winch for retracting the line, andmeans including an index sheave about which the line is wound forcontrolling the length of the increments of travel imparted to themarker.

1. An automated flagger for aircraft engaged in activities wherein theaircraft is caused to over-fly a series of paths extended in parallelismacross a given area comprising: A. a marker for sequentially designatingthe location of each path of said series of paths; and B. meansresponsive to electrical signals for successively repositioning saidmarker.
 2. The flagger of claim 1 wherein said marker includes adisplaceable base, a staff upwardly projected from the base and avisually detectable flag affixed to the distal end thereof.
 3. Theflagger of claim 1 wherein said marker includes a displaceable base, astaff formed of a flexible material upwardly projected from the base,and a radiation emitter affixed to the distal end of said staff.
 4. Theflagger of claim 1 wherein said means for repositioning said markercomprises: A. a fixed base; B. a winch mounted on said base including adrum and an intermittently operable drive train for impartingintermittent driven rotation to said drum; C. a line extended from saidmarker and attached to the drum of said winch, whereby the line isincremently wound about the drum as rotation is intermittently impartedthereto; and D. control means coupled with said drive train forcontrolling the operation thereof.
 5. The flagger of claim 4 whereinsaid control means includes a signal transmitter mounted aboard theaircraft, a signal receiver mounted on said base, a switching circuitconnected with said receiver and said drive train, including meansresponsive to a received signal for activating the drive train.
 6. Theflagger of claim 5 wherein said control means further includes timingmeans coupled with said drive train for deactivating the drive train atthe expiration of a predetermined period of activation.
 7. The flaggerof claim 6 wherein said timing means comprises: A. a sheave of apreselected diameter supported for intermittent rotation between saidwinch and said marker and having said line trained about the peripherythereof, whereby linear displacement of a preselected length of saidline serves to drive said sheave through a complete revolution ofangular displacement as the line is wound about the drum; B. sheavesupport means including an axle and means securing said sheave to saidaxle, whereby the axle is driven in concurrent angular displacement withsaid sheave, bearing means supporting said axle for simultaneous angularand linear displacement, and means responsive to angular displacement ofsaid sheave for cyclically imparting rectilinear motion to said axle;and C. means responsive to an angular displacement of said sheave forinterrupting said switching circuit, including a rotatable timing diskhaving peripheral teeth, drive means having a worm gear mounted on theaxle and meshed with the teeth for driving said disk in rotation, aprotuberance projected from the disk adapted to describe a circular pathas rotation is imparted to the disk, and an actuatable microswitchconnected within said switching circuit, including a switch actuatorinterposed in the path described by said protuberance and engagedthereby as the disk is driven in rotation, whereby the switch isactuated once for each revolution of said sheave.
 8. The flagger ofclaim 7 wherein said means for cyclically imparting rectilinear motionto said axle includes: A. a worm wheel meshed with said worm gear andsupported for rectilinear motion along a path paralleling thelongitudinal axis of said axle; and B. a Pitman arm having one endthereof pivotally fixed to said first worm wheel near the peripherythereof and the opposite end thereof pivotally coupled with said bearingsupport, whereby rotary motion imparted to said sheave as the line iswound about said drum is converted to rectilinear motion and imparted tosaid axle.
 9. An automated flagger for vehicles engaged in activitieswherein a vehicle is caused to traverse a series of substantiallyparallel paths, comprising a marker and means responsive to radiosignals transmitted from the vehicle for imparting uniform increments oftravel to said marker.
 10. The flagger of claim 9 wherein said meansincludes a line attached to the marker, means including a winch forretracting the line, and means including an index sheave about which theline is wound for controlling the length of the increments of travelimparted to the marker.